Navigation Links
Nervous system


The nervous system of an animal coordinates the activity of the muscles, monitors the organs, constructs and processes input from the senses, and initiates actions. (see Central Nervous System).

In animals with brains, the nervous system also generates and conducts thoughts and emotions. Thus it is the system that animates "animals" (sponges are an exception). Chemicals that target the activity of nerves generally are the most rapidly acting toxins, typically causing paralysis and/or death.

Contents

Anatomy

The nervous system consists basically of two types of cells:

  • Neurons are the primary cells of the nervous system
  • Glia are secondary cells involved in nourishment and structural support.

Rapid signalling within the nervous system occurs by two primary mechanisms:

Vertebrate nervous systems

The nervous systems of vertebrate animals are often divided into a central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord. The PNS consists of all other nerves and neurons that do not lie within the CNS. The large majority of what are commonly called nerves (which are actually axonal processes of nerve cells) are considered to be PNS. The peripheral nervous system can also be roughly seen as consisting of sensory pathways and motor pathways , the latter being divided into the somatic (voluntary) nervous system and the autonomic nervous system.

The somatic nervous system is the voluntary part of the nervous system that coordinates a body's movements, such as maintaining a particular posture and walking. The autonomic nervous system is the involuntary part of the nervous system where all of the internal maintenance is taken care of.

The autonomic nervous system is then divided into the sympathetic division and parasympathetic division. The sympathetic nervous system responds to impending danger or stress, and is responsible for the increase of one's heartbeat and blood pressure, among other physiological changes, along with the sense of excitement he feels. The parasympathetic nervous system, on the other hand, is evident when a person is resting and feels relaxed, and is responsible for such things as the constriction of the pupil, the slowing of the heart, the dilation of the blood vessels, and the stimulation of the digestive and geniturinary systems.

Nervous system diversity

The nervous system varies greatly among living animals. Cnidarians, such as sea anemones and jellyfish, have a nerve net, in which the activation of any one neuron triggers a wave of activation across the entire network. These waves are both afferent and efferent, representing both the sensation of chemicals or touch as well as the stimulus of the animals' reflexive mechanical response.The worms and flukes of the phylum platyhelminthes possess a network of nerves that operates like a more conventional nervous system, but lack a brain. Annelid worms and tunicates have a primitive brain called a ganglionic mass, which is a bundle of several nerves. Based in part on commonalities in embryonic development among all chordates, the tunicate brain is believed to resemble the evolutionary precursor of the vertebrate brainstem.

See also


'"/>


(Date:12/17/2014)... 2014  Automation is fundamentally transforming the travel ... at international borders. Over the past decade, ePassports, ... veteran travelers to self process through border control ... at an increasing number of airports, seaports, and ... According to Maxine Most , Principal at ...
(Date:12/11/2014)... WINSTON SALEM, N.C. , Dec. 10, 2014  That ... known for quite a while. Hypertension – the medical term ... disease in the early 1800s, and the inflatable cuff that,s ... That doesn,t, however, mean there,s nothing new about hypertension, ... punctured some long-held beliefs about the condition and the best ...
(Date:12/10/2014)... N.C. , Dec. 9, 2014  Wake Forest Baptist ... education building for its School of Medicine. Funding for ... larger capital campaign that will be publicly launched next ... be located in the former 60 series R.J. Reynolds ... Innovation Quarter. Construction will begin immediately with plans to ...
Breaking Biology News(10 mins):Automated Border Control (ABC) Transforms the Global Travel Experience With More Than 2500 ABC eGates and APC Kiosks Deployed In Airports, Seaports, and Land Borders Worldwide 2Research points to need for new approaches to treatment of high blood pressure 2Research points to need for new approaches to treatment of high blood pressure 3Research points to need for new approaches to treatment of high blood pressure 4Wake Forest Baptist to Build New Medical Education Facility In Wake Forest Innovation Quarter 2Wake Forest Baptist to Build New Medical Education Facility In Wake Forest Innovation Quarter 3Wake Forest Baptist to Build New Medical Education Facility In Wake Forest Innovation Quarter 4
... children with cerebral palsy is crucial to improve ... in sitting balance between children with cerebral palsy ... balance between children with diplegic and hemiplegic cerebral ... Laboratory of Human Motor Control, Faculty of Health ...
... batteries to flat-screen televisions, rely on materials known as rare ... are reporting development of a new method to recycle them ... in the journal ACS Applied Materials & Interfaces , ... industry. Zhang Lin and colleagues point out that ...
... the change of the seasons. After a winter pause, plants ... a new correlation to light: The colder the winter, the ... can be expected as the climate changes, the spring development ... giving an advantage to shrubs and invasive trees that ...
Cached Biology News:Recycling valuable materials used in TVs, car batteries, cell phones 2Warm winters let trees sleep longer 2
Other biology definitionOther Tags